Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$134.96	12.182%	$151.4008	$151.40	$151.40	$151.40
Purchase #2	$85.44	11.483%	$95.2511	$95.25	$95.25	$95.30
Purchase #3	$211.86	13.352%	$240.1475	$240.15	$240.15	$240.10
Purchase #4	$78.49	8.611%	$85.2488	$85.25	$85.25	$85.20
Purchase #5	$250.43	9.772%	$274.902	$274.90	$274.90	$274.90
Purchase #6	$132.53	13.476%	$150.3897	$150.39	$150.40	$150.40
Purchase #7	$108.46	4.263%	$113.0836	$113.08	$113.10	$113.10
7 purchase totals =	$1,002.17		$1,110.4235	$1,110.42	$1,110.45	$1,110.40